Microphone devices are used properly according to their applications such as for music, conference, video camera, and the like. As one of the microphone devices used in a conference hall etc., a gooseneck microphone device has generally been used. FIG. 4 shows one example thereof.
According to this example, for the gooseneck microphone device, a microphone unit 10 is installed on a table via a column 20 including a flexible pipe 21 and a metallic support pipe 22, so that the microphone unit 10 can be adjusted to a proper position with respect to a sound source (speaker) by the flexibility of the flexible pipe 21.
In this example, the microphone unit 10 is held at the distal end of the support pipe 22, and the flexible pipe 21 is interposed between the support pipe 22 and a rotating pedestal 23 supported rotatably on a base, not shown, fixed on a table. For some gooseneck microphone units, the flexible pipe 21 and the support pipe 22 are replaced with each other in arrangement; specifically, the microphone unit 10 is held at the distal end of the flexible pipe 21, and the support pipe 22 is interposed between the flexible pipe 21 and the rotating pedestal 23.
Also, as described in Patent Document 1 (Japanese Utility Model Application Publication No. H05-97191), there has been disclosed a gooseneck microphone device in which the flexible pipe 21 is connected to both ends of the support pipe 22. Further, for some gooseneck microphone devices, the lower end of the flexible pipe 21 or the support pipe 22 is inserted in and fixed to the base without the use of the rotating pedestal 23.
As is well known, the flexible pipe 21 is manufactured by forming a coil spring for generating a restoring force by a round wire such as a steel wire and by inserting a triangular wire consisting of a copper alloy, which has a triangular cross section and is plastically deformed, in a gap between the coil springs. According to this configuration, since the round wire and the triangular wire have high friction, the flexible pipe 21 can be deformed to an arbitrary position, and the deformed state is self-held.
The flexible pipe 21 is cut to a length in accordance with the design drawing, and is connected to the support pipe 22 via a sleeve-form connector 31. Also, the rotating pedestal 23 is provided with a connector (socket) 32 for connecting the flexible pipe 21 to the rotating pedestal 23 by inserting the end portion of the flexible pipe 21 therein.
When the flexible pipe 21 is cut, the coil comes unwound and the end portion thereof spreads out. The amount of spreading is proportional to the amount of unwinding, and the amount of unwinding is not fixed, so that the connectors 31 and 32 are designed so that the inside diameters thereof are large with a margin.
Therefore, when the end portion of the flexible pipe 21 is inserted into the connectors 31 and 32, a wide gap is produced, so that it is necessary to connect the flexible pipe 21 electrically and mechanically to the support pipe 22 and the rotating pedestal 23 by filling this gap.
Specifically, since an electrical cable, not shown, connected to the microphone unit 10 is inserted into the column 20, unless the whole of the column 20 is shielded, noise from the outside may intrude into the electrical cable due to electrostatic connection.
Especially in the case of a condenser microphone, a signal line that is unbalanced with a power line is inserted as the electrical cable. Therefore, unless the whole of the column 20 is shielded, noise may be generated by the intrusion of electromagnetic waves.
Conventionally, therefore, a conductive adhesive has been packed between the end portions of the flexible pipe 21 and the connectors 31 and 32 to secure electrical connection, and besides, for example, an epoxy adhesive has been used to provide mechanical connection strength.
However, since metal powder such as silver is incorporated in the conductive adhesive, displacement after curing changes the electrical resistance, and thereby noise may be generated. Also, the conductive adhesive has a property that the cured adhesive is very hard and brittle to shock.
To compensate this brittleness, the epoxy adhesive having a high bonding strength is used as described above. However, because of high bonding strength, the epoxy adhesive has a problem as described below. When the microphone device is used by being installed on a table, vibrations applied to the table is easily propagated to the microphone unit 10 via the column 20. The vibration noise increases because the mechanical connection becomes tighter as the connecting portion between the flexible pipe 21 and the connectors 31 and 32 is strengthened.